The present invention relates to an improvement in the design of the cooling fan used in personal computers (herein after, PC) today to cool the central processing unit (herein after, CPU). More specifically, to the use of a fan speed monitor which constantly checks the rotational speed of the cooling fan and which will provide warnings of any improper operational variances.
A CPU cooling fan maintains the temperature of the CPU within safe limits. If the rotational speed of the fan slows to below a minimum value the CPU will overheat. A fan running at speeds in excess of a maximum value may indicate an impending fan failure which will lead to the overheating of the CPU. The result of overheating the CPU on the operation of the PC is unpredictable and often times will cause errors in the operation of the PC which may lead the user to blame bugs in the software. In certain systems fan failures or anomalies may even lead to permanent damage of the CPU. As system CPU""s and the design of the fan or heat sinks used on the CPU can vary greatly, the minimum safe speed of the cooling fan may also vary on the make and model of the PC being used.
Current CPU fan detectors either operate on detecting the CPU temperature or on controlling the cooling fan speed and provide an indication of cooling fan failure after it has failed or the temperature of the CPU is too high. This is clearly an undesirable situation and some form of early detection of eminent cooling fan failure is needed.
Additionally, available CPU fan operation detectors do not have memory, which means that they can only indicate the current operating conditions of the cooling fan. This means that if the fan momentarily fails, for however long, and self corrects, this condition is not recognized by the operator unless he is present during this failure. This is also an undesirable situation and a system with memory which will alert the operator of such intermittent failures is needed.
It is the primary objective of the present invention to provide a method of monitoring the operation of a CPU cooling fan at all times that a PC is running.
It is an additional objective of the present invention to provide such a method which will warn a PC user of variances in the operation of the cooling fan.
It is still a further objective of the present invention to provide such a method of warning a PC user of such occurrences that contains a memory feature that will keep track of cooling fan variances which will enable a user to be aware of them whether or not they are using the machine during the time of the fan variance.
These objectives are accomplished by the use of a cooling fan monitor which provides an early warning of impending fan failure. The fan monitor is microprocessor based and has two operating modes: the characterization mode; and the monitor mode. When the present device is first used it will be in the characterization mode. In this mode data is gathered about the operating characteristics of the CPU fan. In the characterization mode, the microcontroller detects the normal operating range of the CPU fan, which is in general PC dependent. The fan speed monitor saves this information in nonvolatile memory for use during the monitor mode. Typically the cooling fan monitor will be left in the characterization mode for sufficent length of time to allow data to be gathered in both high use and low use time periods. The cooling fan monitor is then manually switched, by depressing a button, to the monitor mode. In the monitor mode, the fan speed monitor indicates whether the CPU cooling fan is operating within its normal operating range or if it is operating outside of this range. If the CPU cooling fan goes outside of this normal operating range, the fan speed monitor remembers this condition and indicates the anomaly until it is reset by the operator. This anomaly may be transmitted by various indicators depending upon the severity of the anomaly. This is typically done by setting given ranges. For example Range A might be reached when ever the fan speed varies by a factor of 10%, Range B may be reached when the fan speed varies by 20%. As higher ranges are reached different levels of of severity may be indicated to user, these ranges may vary greatly depending upon a particular users needs and system tolerance. If power is interrupted to the system, the cooling fan monitor will retain its current state thus, when the power resumes the monitor will resume in the state it was in at the time of the power outage.
The fan speed monitor determines the CPU cooling fan speed by monitoring current glitches (which are a function of rotational fan speed) in the fan current. The glitches interrupt the microcontroller which counts the number of such glitches over a specified period of time to determine the rotational fan speed. The fan current is converted to a voltage by passing it through a resistor in series with the fan. Thus, the current glitches are detected as voltage glitches. These voltage glitches are passed through a comparator circuit, which in turn interrupts the processor.
The present invention is equipped with a series of indicator lights and an audible annunciator which convey the information gathered by the fan speed monitor to the PC user. The speed visual indicators may be red, yellow, and green and indicate the current and past speed of the fan motor since the fan speed monitor was last reset. The operation of the indicator lights and audible annunciator may be typically as follows:
For a better understanding of the present invention reference should be made to the drawings and the description in which there are illustrated and described preferred embodiments of the present invention.